Loss of sensory hair cells is a major cause of hearing impairment and can arise from both genetic and environmental causes including noise trauma, aging, and drug exposure. The overall objective of this application is to investigate the mechanism of aminoglycoside drug toxicity in hair cells. This research will test the hypothesis that perturbation of proteins which are direct or indirect targets of aminoglycosides will alter the degree of hair cell death using the zebrafish lateral line as a model system. Two approaches are used to define components modulating aminoglycoside toxicity: physiological alteration of hair cells in wildtype zebrafish and isolation of mutants with altered aminoglycoside response. The specific aims of this application are to: 1) test whether disruption of mitochondrial function alters aminoglycoside response; 2) determine the molecular nature of the zebrafish sentinel mutation that exhibits aminoglycoside resistance; and 3) identify new mutations with sensitivity or resistance to aminoglycoside hair cell loss. The long term goal of this research to identify pathways which may underlie other less experimentally tractable forms of hair cell loss, such as age or noise related hair cell loss, and to suggest targets for intervention during drug treatment.